Vacuum pumps capable of creating such pressures include diffusion and turbomolecular pumps. One of the problems in making such a pump and in making a vacuum pumping apparatus incorporating such a pump, is the selection of materials out of which the components of the pump and apparatus are to be made. Many materials which it would be otherwise desirable to use in the components outgas in a high vacuum at such a rate is to prevent the achievement of a desired degree of vacuum in the chamber to be evacuated. Accordingly, components that are to be exposed to high vacuum in use are typically made of metals such as stainless steel and aluminium, and in particular, components made of plastic materials are rarely if ever used in a high vacuum environment and thus advantages such as a reduction in the cost and weight of the vacuum apparatus typically associated with the use of plastics materials are not achieved.